Subject: Re: [PATCH v1] qlcnic: prevent ->dcb use-after-free on qlcnic_dcb_enable() failure

From: Michal Swiatkowski <[email-masked]>
Date: Tue, 20 Dec 2022 14:32:41 +0100

On Tue, Dec 20, 2022 at 03:56:49PM +0300, Daniil Tatianin wrote:
> adapter->dcb would get silently freed inside qlcnic_dcb_enable() in
> case qlcnic_dcb_attach() would return an error, which always happens
> under OOM conditions. This would lead to use-after-free because both
> of the existing callers invoke qlcnic_dcb_get_info() on the obtained
> pointer, which is potentially freed at that point.
> 
> Propagate errors from qlcnic_dcb_enable(), and instead free the dcb
> pointer at callsite.
> 
> Found by Linux Verification Center (linuxtesting.org) with the SVACE
> static analysis tool.
> 
> Signed-off-by: Daniil Tatianin <[email-masked]>

Please add Fix tag and net as target (net-next is close till the end of
this year)

> ---
>  drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c | 9 ++++++++-
>  drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h       | 5 ++---
>  drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c      | 9 ++++++++-
>  3 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c
> index dbb800769cb6..465f149d94d4 100644
> --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c
> +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c
> @@ -2505,7 +2505,14 @@ int qlcnic_83xx_init(struct qlcnic_adapter *adapter)
>  		goto disable_mbx_intr;
>  
>  	qlcnic_83xx_clear_function_resources(adapter);
> -	qlcnic_dcb_enable(adapter->dcb);
> +
> +	err = qlcnic_dcb_enable(adapter->dcb);
> +	if (err) {
> +		qlcnic_clear_dcb_ops(adapter->dcb);
> +		adapter->dcb = NULL;
> +		goto disable_mbx_intr;
> +	}

Maybe I miss sth but it looks like there can be memory leak.
For example if error in attach happen after allocating of dcb->cfg.
Isn't it better to call qlcnic_dcb_free instead of qlcnic_clear_dcb_ops?

> +
>  	qlcnic_83xx_initialize_nic(adapter, 1);
>  	qlcnic_dcb_get_info(adapter->dcb);
>  
> diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h
> index 7519773eaca6..e1460f9c38bf 100644
> --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h
> +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_dcb.h
> @@ -112,9 +112,8 @@ static inline void qlcnic_dcb_init_dcbnl_ops(struct qlcnic_dcb *dcb)
>  		dcb->ops->init_dcbnl_ops(dcb);
>  }
>  
> -static inline void qlcnic_dcb_enable(struct qlcnic_dcb *dcb)
> +static inline int qlcnic_dcb_enable(struct qlcnic_dcb *dcb)
>  {
> -	if (dcb && qlcnic_dcb_attach(dcb))
> -		qlcnic_clear_dcb_ops(dcb);
> +	return dcb ? qlcnic_dcb_attach(dcb) : 0;
>  }
>  #endif
> diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
> index 28476b982bab..36ba15fc9776 100644
> --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
> +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
> @@ -2599,7 +2599,14 @@ qlcnic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  			 "Device does not support MSI interrupts\n");
>  
>  	if (qlcnic_82xx_check(adapter)) {
> -		qlcnic_dcb_enable(adapter->dcb);
> +		err = qlcnic_dcb_enable(adapter->dcb);
> +		if (err) {
> +			qlcnic_clear_dcb_ops(adapter->dcb);
> +			adapter->dcb = NULL;
> +			dev_err(&pdev->dev, "Failed to enable DCB\n");
> +			goto err_out_free_hw;
> +		}
> +
>  		qlcnic_dcb_get_info(adapter->dcb);
>  		err = qlcnic_setup_intr(adapter);
>  
> -- 
> 2.25.1
>